Kronborg Castle is situated near the town of Elsinore (Danish Helsingør) on the extreme tip of Zealand at the narrowest point of the Oresund (Danish Øresund), the sound between Denmark and Sweden. In this part, the sound is only four kilometres wide, hence the strategic importance of maintaining a fortress at this location. The castle has for centuries been one of the most important Renaissance castles in Northern Europe and was added to UNESCO's World Heritage Sites list on November 30 2000.

The castle's story dates back to a fortress, Krogen, built in the 1420s by the Danish king, Eric of Pomerania. The king insisted on the payment of sound dues by all ships wishing to enter or leave the Baltic; to help enforce his demands, he built a powerful fortress controlling the sound. It then consisted of a number of buildings inside a surrounding wall.

Kronborg acquired its current name in 1585 when it was rebuilt by King Frederick II into a magnificent renaissance castle unique in its appearance and size throughout Europe.

In 1629, a moment's carelessness by two workmen caused much of the Castle to go up in flames. Only the Chapel was spared by the strength of its arches. King Christian IV put great efforts into restoring the castle and by 1639 the exterior was magnificent once again but the interior never fully regained its former glory.

The Swedish conquest of Kronborg in 1658, by Wrangel, demonstrated that the Castle was far from impregnable. Afterwards, the defences were strengthened significantly. From 1688-90, an advanced line of defence was added called the Crownwork . Shortly afterwards, a new series of ramparts were built around it. After their completion, Kronborg was considered the strongest fortress in Europe.

From 1739 until the mid-19th century, Kronborg was used as a slave prison. The inmates were guarded by the soldiers billeted in the Castle. The slaves were male convicts who had been sentenced to work on the Castle's fortifications. The convicts were divided into two categories. Those with minor sentences were categorised as "honest" and were allowed to work outside the Castle walls. Those serving sentences for violence, murder, arson or the like were categorised as "dishonest" and had to serve the full sentence doing hard physical labour inside the Castle ramparts. Otherwise, they served their time under the same conditions: they all had to wear chains and spend nights in cold and damp dungeons.

As Kronborg's importance as a royal castle diminished, the armed forces came to play a greater role. From 1785 to 1922, the Castle was completely under military administration. During this period, a number of renovations were completed.

Kronborg is known by many also as "Elsinore," the setting for much of William Shakespeare's famous tragedy Hamlet, Prince of Denmark. Hamlet was performed in the actual castle for the first time to mark the 200th anniversary of the death of William Shakespeare, with a cast consisting of soldiers from the castle garrison. The stage was in the telegraph tower in the southwest corner of the castle. The play has since been performed several times in the courtyard and at various locations on the fortifications.